Predictive Modelling Methodologies for Bi-material Strip Warpage

Predicting strip warpage after molding process is a challenge for IC packaging industry because simulation tools need to consider multiple processes and complex material properties. This paper conducted a strip warpage experiment and simulation. To simplify this problem, the models are two bi-material strips (epoxy and copper). Two strip processes included transfer and curing. One of the strips contained an additional post mold cure (PMC) process. The strips were then exposed to a reflow process, and the warpage was measured in this process. Pressure-volume-temperature-cure (PVTC) effect and visco-elastic (VE) with two steps shift factor model of Arrhenius and WLF (Williams-Landel-Ferry) functions were considered in the epoxy material model. Fluid mechanics, curing kinetics, heat transfer, and structure analysis were combined in the analysis sequence. The simulation results were compared with the experiment metrics.